Why you can smell the seaside: Source of aromatic molecule behind distinctive coastal scent traced to algal enzyme

[Israel] The fresh, salty smell of the ocean is one of the most distinctive smells on the planet, evoking memories of crashing waves, sandy beaches and the cry of seagulls.

Now scientists have finally unravelled how the seaside odour is produced, tracing it to an enzyme that helps algae survive in their salty seawater environment.

Researchers found the smell itself is produced by algae that form extensive blooms on the ocean surface and release an aromatic compound called dimethylsulfide (DMS) into the air.

This is then blown along with fine spray of sea water onto coastlines around the world.

While scientists identified DMS as the molecule responsible for the distinctive smell of the ocean around eight years ago, exactly how it was produced in the ocean was unclear.

The molecule is known to play an important role in cloud formation and also provides a powerful signal to seabirds to help attract them to the ocean while it also helps fish find the plankton they need to eat.

Blooms of the algae Emiliania huxleyi, like the one shown above in the Barents Sea, can produce 10 million tons of the aromatic chemical dimethylsulfide, which gives the seaside its distinctive smell, every year
Blooms of the algae Emiliania huxleyi, like the one shown above in the Barents Sea, can produce 10 million tons of the aromatic chemical dimethylsulfide, which gives the seaside its distinctive smell, every year

Researchers at the Weizmann Institute of Science in Rehovot, Israel, now claim to have finally traced how it is produced.

Writing in the journal Science, the team led by Dr Uria Alcolombri, a biologist at the Weizmann Institute, said they have found an enzyme that converts another chemical called dimethylsulfoniopropionate (DMSP) to DMS.

They wrote: ‘The volatile DMS is generated in oceans at remarkably high amounts, greater than 10 million tons per year.

‘It is emitted to the atmosphere by enzymes known as DMSP lysases and has a global role in atmosphere-ocean feedback processes.

‘We identified and characterised Alma1, a DMSP lysase from the bloom forming algae Emiliania huxleyi.’

The researchers added the gene appears to be present in many other marine organisms including seaweeds that also release DMS.

This may help to explain why so many plants that grow under the ocean or along the coastline have such a distinctive seaside odour.

It is thought the chemical helps cells survive the changes in salinity in the water around them, which can cause the cells to swell and shrink with water.

But the researchers found that even different species of the Emiliania huxleyi algae produce the molecule with varying efficiency as a result of different levels of expression of the Alma1 enzyme gene.

The single celled phytoplankton Emiliania huxleyi, shown above under an electron microscope, uses an enzyme called Alma1 to produce the aromatic compound DMS and release it into the atmosphere
The single celled phytoplankton Emiliania huxleyi, shown above under an electron microscope, uses an enzyme called Alma1 to produce the aromatic compound DMS and release it into the atmosphere

This may explain why on some days the smell of the sea can be stronger than on others as different algae blooms flourish.

Andrew Johnston, a microbial geneticist at the University of East Anglia who was not involved in the study, said the new findings could help scientists unravel the influence life in the sea can have on the weather and wildlife on land.

He said: ‘DMS is a component of the tangy aroma of the seaside and functions as a chemical attractant that guides various marine animals – including some sea birds, invertebrates, and even mammals – toward potential food supplies.

‘Not only does the release of DMS into the atmosphere contribute substantially to the global flux of sulfur from sea to air and back to land via precipitation but also DMS oxidation products act as condensation nuclei, causing water molecules to coalesce, with possible effects on local climate through enhanced cloud formation.’

THE SICKLY ODOUR OF DEATH

Dead bodies give off a distinctive, sickly-sweet odour that’s immediately recognisable and hard to forget.

The smell of death can consist of more than 400 volatile organic compounds in a complex mixture, researchers have revealed.

These compounds are produced by the actions of bacteria, which break down the tissues in the body into gases and salts.

The exact composition of the gas mixture changes as decomposition progresses.

It also varies slightly according to the exact composition of the bacterial population in and around the body and the interactions between them, the climate of the habitat, and to a lesser extent the genetic make-up and diet of the deceased.

The compounds given off can vary, but there may be core compounds with concentrations that change in a consistent way.

If so, analyses of the exact composition of the smell given off by a body could eventually help forensics investigators to estimate the time of death more accurately.

 

Photo: The seaside has an unmistakable aroma that can be detected from miles around, now new research has traced the source of the chemicals that produce this smell to chemicals produced by ocean algae to help them survive in their saltwater environment. The picture above shows spray crashing over the coast of Wales

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